Interferometer system and method for lens column alignment

Abstract

A projection exposure apparatus and method aligns a substrate with an optical axis of a lens column using one or more interferometers, mirrors, and a control device. The lens column projects a pattern from a mask onto the substrate. The optical axis of the lens column is perpendicular to the substrate. To ensure precise alignment of the lens column and the substrate, the one or more interferometers use a plurality of beams having respective paths, the lengths of which change in response to movement of the optical axis. In response to the detected changes of the interferometer beams, a control device adjusts the position of the stage so that the substrate is aligned with the optical axis of the lens column.

Description

A. Field of the InventionThe present invention relates generally to a projection exposure system for transferring an image of a pattern onto a substrate, such as a semiconductor wafer. More particularly, the present invention relates to a projection exposure apparatus and method that provides enhanced precision in the alignment of a projection optical system and the substrate.B. Description of the Prior ArtSemiconductor fabrication requires precise alignment of an optical system with a substrate in order to produce extremely detailed circuitry on the substrate. FIG. 1 illustrates a conventional projection exposure apparatus 10, which includes a light source 12, a stage 14, a lens column 16, a mask 18, and an interferometer 20. Light source 12 illuminates mask 18, causing a pattern from the mask to be projected through lens column 16. Lens column 16 projects the pattern onto a photosensitive substrate on stage 14. The optical axis of lens column 16 is indicated by the broken line dow...

AI Technical Summary

Problems solved by technology

As the beams travel back through the beam splitter they interfere with each other.

Charges in beam 21, however, may not provide accurate information for alignment because of the sensitivity of lens column 16 to thermal expansion and displacement.

More particularly, because conventional alignment procedures use only one side of lens column 16, all of the alignment problems are not properly detected.

Accordingly, the adjustment of stage 14 in relation to lens column 16 is often inaccurate and, as such, results in errors in the projection of the image of the pattern onto the substrate on stage 14.

Typically, adjusting stage 14 results in vibration throughout the projection exposure apparatus.

Accordingly, adjustment of stage 14 in relation to lens column 16 is often inaccurate and results in errors in the projection of the image of the pattern onto the substrate on stage 14.

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